Spindle device using dynamic pressure bearing

Abstract

Disclosed is a spindle device endowed with a sufficient load capacity for bending moment and capable of reducing power loss and heat generation of the main shaft attributable to the radial dynamic pressure bearing. In this spindle device, the rotation of the spindle rotor is supported by a pair of radial dynamic pressure bearing portions, between which there is provided a first cooling chamber so as to circumferentially surround the spindle rotor, atmosphere outside the housing being introduced into the first cooling chamber.

What is claimed is:  
     
       1. A spindle device comprising: a housing; a spindle rotor one end portion of which protrudes from the housing; a pair of radial dynamic pressure bearing portions provided on the spindle rotor at a predetermined axial interval and rotatably supporting the spindle rotor with respect to the housing; a supply flow passage for guiding lubricant to bearing gaps of the radial dynamic pressure bearing portions; a first cooling chamber provided between the pair of radial dynamic pressure bearing portions so as to circumferentially surround the spindle rotor and communicating with the bearing gaps of the radial dynamic bearing portions; and an air inlet adapted to introduce atmosphere outside the housing into the first cooling chamber. 
     
     
       2. A spindle device according to  claim 1 , wherein the peripheral surface of the spindle rotor facing the first cooling chamber is rendered water-repellent. 
     
     
       3. A spindle device according to  claim 1 , further comprising a pair of thrust dynamic pressure bearing portions provided so as to axially sandwich from outside the pair of radial dynamic pressure bearing portions to restrict the spindle motor in its axial movement and to establish communication between bearing gaps of the thrust dynamic pressure bearing portions and the bearing gaps of the radial dynamic pressure bearing portions adjacent thereto, 
       wherein each radial dynamic pressure bearing portion is equipped with dynamic pressure generating grooves for pressurizing lubricant supplied to the bearing gap thereof toward the bearing gap of the thrust dynamic pressure bearing portion adjacent thereto and pressurization discharge grooves for pressurizing the lubricant toward the cooling chamber.  
     
     
       4. A spindle device according to any one of  claims 1  to  3 , wherein there is provided between the spindle rotor and the housing a labyrinth seal portion for sealing the housing from the exterior thereof, the labyrinth seal portion being rendered water-repellent.